Prehistoric Shark Species Found in Ariz.

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The remains of several new toothy shark species, with at least
three dating to 270 million years ago, have been unearthed in
Arizona, according to a new study.

The research, published in the latest issue of Historical
Biology, suggests that Arizona was home to the most diverse
collection of sharks in the world during the pre-dinosaur Middle
Permian era. The researchers have discovered many other new shark
species from the area, with papers in the works to document them.

For now, lead author John-Paul Hodnett described the three
mentioned in the latest study:

Nanoskalme natans ("swimming dwarf blade") was a small
(about 3.2-foot- long) shark with blade-like cutting teeth. It
was probably a scavenger and predator on small fish.

Neosaivodus flagstaffensis ("new Saivodus from
Flagstaff") was a medium-sized shark (about 6.6 feet) with
gripping teeth that might have been a specialist on nautiloids as
a juvenile, but a more generalist feeder as an adult.

Kaibabvenator swiftae ("Swift's Kaibab hunter") was a
large (around 19.7 feet ) shark with big serrated cutting teeth.
It was presumably an active apex predator on large prey including
other sharks, similar to the modern great white shark.

Hodnett, a researcher in the Museum of Northern Arizona's Geology
and Paleontology Department, analyzed the shark remains with
colleagues David Elliott, Tom Olson and James Wittke. The sharks
were unearthed at what is known as the Kaibab Formation of
northern Arizona.

Elliott told Discovery News that a shallow, warm sea covered this
part of Arizona at the time. Today, this same area is a high
plateau region supporting a Ponderosa Pine forest. Although hard
to imagine, the region was once home to a bustling
shark-eat-shark ecosystem.

"At this time, sharks were the main vertebrate predators in
marine environments world wide, and they were very numerous and
diverse, filling niches that were occupied later by bony fish and
even mammals, such as cetaceans (a group that includes whales and
dolphins)," Hodnett said. "The main predators on sharks would
have been other sharks."

According to the researchers, the new species are all
ctenacanthiformes, an extinct order of primitive sharks
characterized by two ornamental dorsal fin spines, and teeth in
which the central cusp is large and well-developed, with smaller
lateral cusps. The sharks' tails were symmetrical, unlike the
asymmetrical tails of most modern sharks, and their heads were
short-snouted.

The findings reveal how rich and diverse marine life was at the
time, some 45 million years before the first dinosaurs even
appeared.

Elliott shared that on land during this period, "the most
important vertebrates were the synapsids (pre-mammals) that
included animals such as Dimetrodon." That was a
lizard-like beast with a large sail on its back.

Sharks, however, clearly ruled Arizona back in the day.

John Maisey, curator and research chair of the Division of
Paleontology at the American Museum of Natural History, told
Discovery News, "The real significance of the paper is in
revealing the considerable diversity shown by these top predators
shortly before their disappearance at the end of the Permian. The
Permian marks a real transition in the shark world, from
'ancient' to 'modern,' and the modern diversity of sharks and
rays only begins in the early Jurassic."

Maisey continued, "It is still not clear whether some sharks,
classified as 'ctenacanths,' actually gave rise to modern
shark-like fishes, or represent a dead-end group; that is
something which may emerge as research continues. This
study is an important step in the process."